Answer:
in controlled experiment an independent variable is systematically manupulated and dependent variable is measured ; any extraneous variables are controlled
Answer:
carbon dioxide passes from the blood into the alveoli and is then exhaled. Oxygenated blood travels from the lungs through the pulmonary veins and the cycle goes on every time you breath or inhale you inhale oxygen into your blood cells.
Explanation:
37 to 42 weeks is the average length of a human pregnancy.
